1. Field of Invention
The present invention relates to a liquid crystal display (LCD) panel. More particularly, the present invention relates to an LCD panel which allows the spacers to have uniform compressing density by applying biased compensation.
2. Description of Related Art
An LCD panel is generally formed by a thin film transistor array substrate (TFT array substrate) and a color filter substrate (CF substrate). A gap has to be sustained between the TFT array substrate and the CF substrate with spacers to fill in a liquid crystal layer between the two substrates. Generally, the spacers are disposed on the CF substrate and are in contact with the TFT array substrate.
However, during assembly process, the spacers of an LCD panel may shift along with the shift of the panel that the area density (i.e. compressing density) of the spacers which is in contact with the TFT array substrate will also be changed. Thus, the gap between the two substrates will not be uniform, which affects the display quality of the panel.
Accordingly, shift stopping and biased compensation are provided in the conventional technology to resolve the problem of the poor display quality resulted from spacer shift. FIGS. 1A and 1B are cross-sectional views of two conventional LCD panels. First, referring to FIG. 1A, the LCD panel 100 includes a TFT array substrate 110, a CF substrate 120, and a liquid crystal layer 130 located between the two substrates. Moreover, the TFT array substrate 110 has a plurality of protrusions 112, and a groove 114 is located between two protrusions 112. It is remarkable that the spacer 140 is disposed on the CF substrate 120 and in contact with the groove 114 to prevent the spacer 140 from moving.
Then, referring to FIG. 1B, the LCD panel 200 also has a TFT array substrate 210, a CF substrate 220, and a liquid crystal layer 230 located between the two substrates. Wherein, there is a drain 212 on the TFT array substrate 210 and a planarized layer 216 covers the drain 212. By fabricating a contact window opening 216a in the planarized layer 216 above the drain 212, the pixel electrode 214 is electrically connected to the drain 212 through the contact window opening 216a. It is remarkable that the spacer 240 is disposed on the CF substrate 220 and locked in the contact window opening 216a to prevent the spacer 240 from moving.
The spacers 140 and 240 can be prevented from moving and further the panels can be prevented from shifting through the shift stopping methods shown in FIGS. 1A and 1B. However, because the external power shifting the panels is generally stronger, the spacers 140 and 240 may be pushed out of the groove 114 or the contact window opening 216a, which may affect the supporting performance of the spacers 140 and 240 and the uniformity of the gap d.
In addition, FIG. 2A is a cross-sectional view of another conventional LCD panel. In the LCD panel 300, a plurality of spacers 344 and 342 (only one is shown) are respectively fabricated on the TFT array substrate 310 and the CF substrate 320, the spacers 344 are partially in contact with the spacers 342 to sustain the gap d of the panel, and the liquid crystal layer 330 is disposed between the two substrates.
FIG. 2B is a top view of the spacers in FIG. 2A. Referring to both FIG. 2A and FIG. 2B, when the CF substrate 320 shifts rightward, the contacting area R1 between the spacers 342 and 344 in the first spacer group A1 is reduced, while the contacting area R2 between the spacers 342 and 344 in the second spacer group A2 is increased, thus the contacting area R1 of the first spacer group A1 and the contacting area R2 of the second spacer group A2 can compensate each other horizontally. Based on the same principle, the contacting area R3 of the third spacer group A3 and the contacting area R4 of the fourth spacer group A4 can compensate each other vertically.
However, the LCD panel 300 as shown in FIGS. 2A and 2B is only applicable when the panel does not shifts too much, that is, the distance the panel shifts is within the range of half the sizes of the spacers 342 and 344. Along with the development of large size panels, the panel shift will increase accordingly. Hence, the methods described above will become ineffective; the problems of unevenness of the compressing density of the spacers, non-uniformity of the panel gap, and poor panel display performance still remain unsolved.